Processing apparatus and processing method

ABSTRACT

The present invention provides a processing apparatus and a processing method, both of which can carry out a low-temperature process to allow active gas species to react with an oxide film on an object to be processed to form a product film and a heating process to heat the object to a predetermined temperature to evaporate the product film, in succession. This processing apparatus  12  is provided with a shielding plate  103  capable of entering a gap between the object W and a transparent window  28  and also withdrawing from the gap. On condition that the shielding plate  103  is closed to cut off irradiation heat from the transparent window  28 , the product film is formed by allowing the active gas species of NF 3  gas to react with a native oxide film on the object under the low-temperature condition. After that, upon closing the shielding plate  103 , the native oxide film is removed by applying heat irradiated from a heating lamp  36  to the product film through the transparent window  28 . Additionally, the apparatus includes a low-temperature processing chamber  207  allowing NF 3  gas to react with the native oxide film at a low temperature and a heating chamber  209  for heating the product film, independently.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a processing apparatus for removing anoxide film from a surface of an object to be processed and also relatesto a processing method of removing the oxide film from the surface.

2. Description of the Related Art

Hitherto, as the method of removing native oxide films in fine holesformed in a wafer effectively, there is a surface treatment method asfollows.

At first, by using of plasma technique, a mixture of N₂ gas and H₂ gasis activated to produce active gas species. Second, NF₃ gas is added tothe down flow of the active gas species in order to activate NF₃ gas.Next, it is executed to allow the active gas species of NF₃ gas to reactwith a native oxide film on the surface of the wafer thereby producing aproduct film. By heating the wafer to a designated temperaturesubsequently, the product film is sublimated for its removal.

As the apparatus used in such a method, there is known a processingapparatus which includes a processing container for accommodating awafer therein, a NF₃ active gas species generating unit for generatingthe active gas species of NF₃ gas, heating means positioned outside theprocessing container in order to heat the wafer and a transparent windowarranged between the heating means and the above object to allow heatenergy from the heating means through. In this apparatus, it is executedto make the active gas species of NF₃ gas to react with the native oxidefilm formed on the surface of the wafer, at a low temperature, therebyforming a product film. Next, by the heating means, the product film isheated to a predetermined temperature for its sublimation, removing thenative oxide film.

In the above processing apparatus, however, if the heating process ofthe wafer has been completed and subsequently, a new wafer is loadedinto the processing container for the low-temperature treatment, thenthe new wafer is undesirably heated due to heat radiated from thetransparent window heated in the previous heating process. Therefore, itis necessary to wait for the transparent window to be cooled to adesignated temperature, thereby causing the processing efficiency to bedeteriorated remarkably.

DISCLOSURE OF THE INVENTION

In order to solve the above problem, the object of the present inventionis to provide a processing apparatus and a processing method, by whichit is possible to prevent the temperature of the object from rising dueto residual heat generated in the heating process and also remained in atransparent window, thereby accomplishing the continuous processing forthe objects to be processed.

In accordance with the first feature of the invention, there is provideda processing apparatus for removing an oxide film from a surface of anobject to be processed, the processing apparatus comprising: aprocessing container accommodating the object to be processed therein;an active gas species generating unit for producing active gas species;heater arranged outside the processing container to heat the object tobe processed; a transparent window formed in the processing containerbetween the heater and the object to be processed, the transparentwindow sheltering the interior of the processing container from theoutside in an airtight manner and also allowing heating energy from theheater to pass through; and a shielding plate provided in such a waythat the shielding plate can be inserted into or extracted from a gapbetween the object and the transparent window; in the processingapparatus, on condition that the shielding plate is closed to insulateirradiation heat irradiated from the transparent window, the processingapparatus allows the oxide film formed on the surface of the object toreact with the active gas species, thereby forming a product film.Subsequently, the processing apparatus opens the shielding plate so asto apply the irradiation heat from the heater to the product filmthrough the transparent window and further heats the product film to apredetermined temperature for vaporization, thereby removing the productfilm.

In accordance with the second feature of the invention, there is alsoprovided a processing apparatus for removing an oxide film from asurface of an object to be processed, the processing apparatuscomprising: a first processing chamber having an active gas speciesgenerating unit for producing active gas species and also allowing theoxide film formed on the surface of the object to react with the activegas species under a condition of low temperature, thereby forming aproduct film; a second processing chamber having heater for heating theobject to be processed and allowing the heater to heat the product filmformed on the surface of the object to a predetermined temperature forvaporization, thereby removing the product film; and transporter fortransporting the object between the first processing chamber and thesecond processing chamber.

In accordance with the third feature of the invention, the active gasspecies are active gas species of NF₃ gas.

In accordance with the fourth feature of the invention, the shieldingplate is provided with cooler for cooling the shielding plate itself.

In accordance with the fifth feature of the invention, the transporteris arranged in a transfer chamber connected to the first processingchamber and the second processing chamber and also filled up with anon-reactive atmosphere inside.

In accordance with the sixth feature of the invention, the active gasspecies generating unit includes a plasma generating tube having aplasma generating part, a plasma gas introducing part for supplying bothN₂ gas and H₂ gas into the plasma generating tube and a NF₃ gassupplying part for adding NF₃ gas to the active gas species flowing downfrom an interior of the plasma generating tube.

In accordance with the seventh feature of the invention, the plasmagenerating part comprises a microwave generating source for generatingmicrowaves and a waveguide for introducing the so-generated microwavesinto the plasma generating tube.

In accordance with the eighth feature of the invention, there is alsoprovided a processing method of removing an oxide film from a surface ofan object to be processed while using a processing apparatus whichincludes a processing container accommodating the object to be processedtherein, heater arranged outside the processing container to heat theobject to be processed, a transparent window formed in the processingcontainer between the heater and the object to be processed, and ashielding plate provided in such a way that the shielding plate can beinserted into or extracted from a gap between the object and thetransparent window, the processing method comprising the steps of:allowing the oxide film formed on the surface of the object to reactwith active gas species under a condition of low temperature oncondition that the shielding plate is closed to insulate irradiationheat irradiated from the transparent window, thereby forming a productfilm; and subsequently, opening the shielding plate and applying theirradiation heat from the heating means to the product film through thetransparent window to heat the product film to a predeterminedtemperature for vaporization, thereby removing the product film.

In accordance with the ninth feature of the invention, there is alsoprovided a processing method of removing an oxide film from a surface ofan object to be processed, the processing apparatus comprising: allowingthe oxide film formed on the surface of the object to react with activegas species under a condition of low temperature in a first processingchamber, thereby forming a product film; transporting the object havingthe product film formed thereon from the first processing chamber to asecond processing chamber; and heating the product film formed on thesurface of the object in the second processing chamber, to apredetermined temperature for vaporization, thereby removing the productfilm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view showing a processing apparatus in accordancewith the first embodiment of the present invention;

FIG. 2 is a schematic plan view taken along a line II-II of FIG. 1,showing a movable shutter of the processing apparatus of FIG. 1;

FIG. 3 is a schematic sectional view taken along a line III-III of FIG.2;

FIG. 4 is a schematic plan view showing another movable shutter; and

FIG. 5 is a structural view showing the processing apparatus inaccordance with the second embodiment of the present invention.

BEST MODE OF EMBODIMENTS OF THE INVENTION

Preferred embodiments for embodying the processing apparatus of thepresent invention will be described with reference to figures, below.

FIGS. 1 to 3 are structural views showing the processing apparatus inaccordance with the first embodiment of the invention. In FIG. 1, theprocessing apparatus 12 includes a plasma generating tube 14 foractivating a mixture gas of N₂ gas and H₂ gas by plasma, and aprocessing container 16 for carrying out a designated surface treatmentfor removing an oxide film particularly, a native oxide film (i.e. oxidefilm unintentionally produced by the contact with oxygen in the air,cleaning liquid, etc.) from a semiconductor wafer W as the object to beprocessed.

The processing container 16 is in the form of a cylinder made ofaluminum. In the processing container 16, there is a quartz mount 20carried by a support member 18 which is movable up and down. Theprocessing container 16 is provided, on the margin of a bottom thereof,with an exhaust port 22 allowing the interior of the container 16 to beevacuated. Below the mount 20, an irradiation port 26 is formed on thebottom part of the processing container 16 and a quartz transparentwindow 28 is fitted to the irradiation port 26 in an airtight manner.Below the transparent window 28, a number of heating lamps 36, such ashalogen lamps, are arranged to heat the mount 20 from the underside, sothat heating light emitted from the healing lamps 36 permeates throughthe transparent window 28 and enters into the back face of the wafer W.

On the other hand, the plasma generating tube 14 in the form of a tubemade of e.g. quartz is fitted to the processing container 16 in anairtight manner. Further, the plasma generating tube 14 is arranged soas to stand on the container 16 while opening into the ceiling part ofthe container 16. The plasma generating tube 14 is provided, at a topend thereof, with a plasma-gas ejecting part 44 for introducing a plasmagas consisting of N₂ gas and H₂ gas into the tube. The plasma-gasejecting part 44 is equipped with an ejection nozzle 46 inserted intothe inside of the plasma generating tube 14 and connected to a gaspassage 48. While, through respective flow control units 50 like matercontrollers, the gas passage 48 is connected to a N₂ gas source 52 forstoring N₂ gas and a H₂ gas source 54 for storing H₂ gas, respectively.

A plasma generating part 56 is arranged just below the ejection nozzle46. The plasma generating part 56 comprises a microwave generatingsource 58 generating a microwave of 2.45 GHz and a microwave supplier60, such as an Ebenson-type waveguide, arranged in the plasma generatingtube 14, so that the microwave generated in the microwave generatingsource 58 is supplied into the microwave supplier 60 through arectangular waveguide 62. Then, the so-supplied microwave allows plasmato be produced in the plasma generating tube 14 and therefore, themixture of H₂ gas and N₂ gas is activated to form a down flowing of themixture.

At an outlet 64 identical to the lowermost end of the plasma generatingtube 14, there is communicably provided a quartz cover member 66diverging downward in the form of an umbrella, which covers the upwardof the mount 20 thereby to drop a gas on the wafer W effectively. Justbelow the outlet 64, a NF₃ gas supplier 68 is arranged to supply NF₃ gasto the wafer. The NF₃ gas supplier 68 has an annular shower head 70 madeof quartz and provided with numerous gas orifices 72. The shower head 70is connected to a NF₃ gas source 80 storing NF₃ gas, through acommunication tube 74, a gas passage 76 and a flow controller 78.

In the structure mentioned above, a movable shutter 101 is disposedbetween the mount 20 and the transparent window 28. The movable shutter101 has a shielding plate 103 rotatably arranged so as to cover thetransparent window 28, as shown in FIGS. 2 and 3. The shielding plate103 is provided with a rotating shaft 105 to penetrate an outer wall 107of the processing container 16 in order to rotate the plate 103. Betweenthe rotating shaft 105 and the outer wall 107, a magnetic fluid seal 109is arranged to hold the rotating shaft 105 tightly but rotatably to theouter wall 107. The rotating shaft 105 is equipped with a shaft gear 111meshing with a motor gear 113 of a drive motor 115.

With the operation of the drive motor 115, it allows the shielding plate103 to rotate through the shaft gear 111 and the motor gear 113, so thatthe plate 103 can occupy its opening position of FIG. 2 and the closingposition of FIG. 3.

A coolant passage 117 is formed inside the shielding plate 103 and alsothe rotating shaft 105. Extending from the lower end of the rotatingshaft 105 to the exterior of the processing container 16, the coolantpassage 117 is connected to a coolant circulating means 119 arrangedoutside the processing container 16. When the coolant circulating means119 supplies the coolant passage 117 with a coolant, such as water, theshielding plate 103 can be cooled down. With the arrangement mentionedabove, it is possible to prevent the temperature of the shielding plate103 from being elevated by radiant heat irradiated from the transparentwindow 28. Accordingly, the radiant heat from the shielding plate 103can be prevented from reaching the wafer W thereby to avoid rising thetemperature of the wafer W.

Meanwhile, FIG. 4 is a view of an example of another movable shutter121. The movable shutter 121 includes a shielding plate 123 for coveringthe transparent window 28. Connected with the shielding plate 123 aretwo drive shafts 125, 125 which has their other ends connected to apiston rod of a hydraulic cylinder 127. Further, in the processingcontainer 16 where the drive shafts 125, 125 penetrate an outer wall129, respective magnetic fluid seals 131 are arranged between the driveshafts 125, 125 and the outer wall 129, allowing the shafts 125, 125 tomove in relation to the outer wall 129 while maintaining respective gapsbetween the shafts 125, 125 and the outer wall 129 in airtight manner.In this way, the operation of the hydraulic cylinder 127 allows theshielding plate 123 to occupy its opening position and the closingposition.

Also in this case, similarly to the case of FIG. 3, the shielding plate123 and the drive shafts 125 may be provided, inside thereof, withcoolant passages while their ends outside the processing container 16are connected with a coolant circulating means arranged outside theprocessing container 16 to allow the shielding plate 123 to be cooled.With this structure, it is possible to restrain the temperature of thewafer W from be elevated by the radiant heat from the shielding plate123.

Next, we explain a removing method of the native oxide film, which isperformed by the apparatus constructed above. First, load thesemiconductor wafer W as an object to be processed into the processingcontainer 16 via a not-shown gate valve and put the wafer W on the mount20. In this wafer W, there exist contact holes etc. formed in e.g. thepreceding stage, while the native oxide film is generated on each bottomof the contact holes.

After loading the wafer W in the processing container 16, close up thechamber 16 tightly and subsequently evacuate it. Then, introduce N₂ gasand H₂ gas, which have been fed from the N₂ gas source 52 and the H₂ gassource 54 respectively, into the plasma generating tube 14 through theplasma-gas ejecting part 44, at predetermined flow rates.Simultaneously, generate the microwave of 2.45 GHz by the microwavegenerating source 58 of the plasma generating part 56 and introduce themicrowave into the plasma generating tube 14 via the microwave supplier60. Consequently, by the microwave, both N₂ gas and H₂ gas are activatedand changed into plasmatic gases to form active gas species. Theseactive gas species form their down flow by the evacuation in theprocessing container 16 and fall in the plasma generating tube 14 towardthe outlet 64.

On the other hand, NF₃ gas supplied from the NF₃ gas source 80 is addedto the down flowing active gas species of the mixture gas composed of N₂gas and H₂ gas, through the annular shower head 70. As a result, theso-added NF₃ gas is also activated by the down flowing active gasspecies. In this way, NF₃ gas is activated to react with the nativeoxide film on the surface of the wafer W in combination with theabove-mentioned down flowing active gas species, thereby producing aproduct film having elements Si, N, H, F mixed therein.

Since this processing is accelerated at low temperature, the wafer Wdoes not have to be heated during the processing and the product film isproduced at room temperature.

Hereat, during the processing, the movable shutter 101 is under theclosed condition. The reason why the shutter closes is to prevent thetemperature of the wafer from being elevated since the radiant heat fromthe transparent window 28 heated in the previous heating process reachedthe wafer W.

As to the processing conditions, the respective flow rates of H₂ gas,NF₃ gas and N₂ gas are equal to 10 sccm, 150 sccm, 1400 sccm,respectively. The other conditions are respectively 4 Torr in processingpressure, 400 W in plasma voltage, and 1 minute in processing time. Inthis way, it is carried out to form the product film reacting with thenative oxide film on the wafer surface. In this case, since the upsideof the mount 20 is covered with the cover member 66 in the form of anumbrella, the down flowing active gas species flow down on the wafersurface effectively without dispersing to the circumference, so that theproduct film can be completed effectively.

When the formation of the product film is completed in this way, stoprespective supplies of H₂ gas, NF₃ gas and N₂ gas and likewise thedriving of the microwave generating source 58 and thereupon, theprocessing container 16 is evacuated to discharge residual gas.Subsequently, bring the movable shutter 101 to the opening position andlight the heating lamp 36 to heat the wafer W into a predeterminedtemperature, for example, more than 100° C. Owing to this heating, theabove product film is sublimated for its vaporization. Thus, the nativeoxide film on the wafer W is eliminated, so that a Si-surface appears onthe wafer surface. Then, the processing conditions are 1 mTorr inprocessing pressure and the order of 2 minutes in processing time.

As mentioned above, the processing apparatus is provided, between thewafer W and the transparent window 28, with the movable shutter 101capable of entering and withdrawing. Therefore, when the active NF₃ gasreacts with the native oxide film on the wafer surface to produce theproduct film having elements Si, N, H, F mixed therein, namely, at theprocessing at low temperature, it is possible to prevent the wafer Wfrom being heated by the radiant heat emitted from the transparentwindow 28 heated in the previous heating process. Accordingly, in caseof repeating the above “low temperature” treatment and the heatingtreatment against a plurality of wafers by turns, it is possible toprevent the wafer during the low temperature treatment from being heatedby the radiant heat due to the previous heating treatment. Therefore,the low temperature treatment and the heating treatment can besuccessively carried out with no interval, accomplishing the removaloperation of the oxide film effectively.

In the movable shutter of the processing apparatus, since the motor 115outside the processing container and the shielding plate 103 inside thecontainer are connected with each other by the rotating shaft 105 sealedby the magnetic fluid seal 109, there is no need to provide any drivingmeans in the processing container, whereby it can be small-sized withthe prevention of contamination.

Such operation and effect are similar to the reciprocating movableshutter 121 of FIG. 4.

FIG. 5 shows the second embodiment of the present invention. Aprocessing apparatus 201 is characterized to have a low-temperatureprocessing chamber and a heating chamber independently. The processingapparatus 201 is provided, at a center thereof, with a transfer chamber203. In the transfer chamber 203, there is a transfer device fortransporting the wafer. At the interior of the transfer chamber 203,there is established a non-reactive atmosphere, for example, vacuumwhich can prevent the occurrence of native oxide film on the wafer Wduring the transportation of wafer W. In the transfer chamber 203, aload locking chamber 205 is provided in order to load the wafer to beprocessed into the transfer chamber 203.

While, on the opposite side of the transfer chamber 203 to the loadlocking chamber 205, there are provided two low-temperature processingchambers 207, 207. Each low-temperature processing chamber 207substantially corresponds to the processing apparatus 12 of FIG. 1 whileremoving the movable shutter 101 and the heating lamp 36. Then, althoughit is necessary that the processing container 16 has its bottom closedtightly, a member for closing the bottom of the container 16 doesn'thave to be provided with such light-permeability as the transparentwindow 18 of FIG. 1. Thus, for example, an aluminum plate in place ofthe transparent window 28 of FIG. 1 may close the bottom of theprocessing container 16. In this low-temperature processing chamber 207,the active NF₃ gas reacts with the native oxide film on the wafersurface to produce the product film having elements Si, N, H, F mixedtherein.

Again, the transfer chamber 203 is provided with a heating chamber 209.In the heating chamber 209, there is provided heating means, forexample, a well-known stage heater of resistance heating type, whichallows the wafer W to be heated. In the heating chamber 209, the wafer Wafter the low-temperature treatment is heated to a predeterminedtemperature, for example, more than 100° C. Owing to this heating, theabove product film is sublimated for its vaporization. Thus, the nativeoxide film on the wafer W is eliminated.

The transfer chamber 203 further includes a cooling chamber 211. Thiscooling chamber 211 serves to cool the wafer after the heatingtreatment. Despite that the processed wafer is unloaded while beingaccommodated in a resinous cassette, there is the possibility of theresin cassette being damaged by the wafer of high temperature.Therefore, the apparatus is constructed so as to cool the wafer beforeit is accommodated in the cassette.

In the so-constructed processing apparatus 201, the wafer having thenative oxide film formed thereon is transported from the load lockingchamber 205 into the transfer chamber 203. Next, the wafer istransported to the low-temperature processing chamber 207 where theso-called low-temperature treatment is carried out. Since the processingapparatus 201 has the heating chamber 209 arranged independently of thelow-temperature processing chamber 207, it is possible to prevent theresidual heat in the previous heating process from exerting a badinfluence on the low-temperature treatment. After that, the wafer to beprocessed is fed to the heating chamber 209. In the heating chamber 209,the wafer W after the low-temperature treatment is heated to adesignated temperature, for example, more than 100° C. to sublimate(evaporate) the above product film. Consequently, the native oxide filmon the wafer W is removed. Thereafter, the so-heated wafer is fed to thecooling chamber 211. After being cooled, the wafer is accommodated inthe cassette and discharged from the chamber 211. Accordingly, it ispossible to prevent the wafer of high temperature from damaging theresinous cassette.

As mentioned above, since the processing apparatus 201 has thelow-temperature chamber 207 and the heating chamber 209 arrangedindependently of each other, it is possible to prevent the wafer frombeing heated due to the influence of heating process when the active NF₃gas reacts with the native oxide film on the wafer to produce theproduct film having Si, N, H, F mixed therein, in other words, at thelow-temperature treatment. Thus, the low-temperature treatment and theheating process can be continuously performed with no interval, so thatit is possible to accomplish the oxide film removing operationeffectively.

According to the invention, there is provided the shielding plate whichis adapted so as to enter the gap between the object and the transparentwindow and also withdraw from the gap. Therefore, the closing of theshielding plate makes it possible to insulate the heat irradiated fromthe transparent window and also allows the active gas species to reactwith the oxide film under the low-temperature condition. Further in thepresent invention, the low-temperature treatment allowing the active gasspecies to react with the oxide film is carried out in a differentchamber from that of the subsequent heating process. Accordingly, thelow-temperature treatment and the heating process can be continuouslyperformed with no interval, so that it is possible to accomplish theoxide film removing operation effectively.

1-9. (canceled)
 10. A processing method of removing an oxide film from asurface of an object to be processed while using a processing apparatuswhich includes: a processing container accommodating the object to beprocessed therein, an active gas species generating unit for producingactive gas species, a heater arranged outside the processing containerto heat the object to be processed, a transparent window formed in theprocessing container between the heater and the object to be processed;and a shielding plate provided in such a way that the shielding platecan be inserted into or extracted from a gap between the object and thetransparent window, the processing method comprising the steps of:conveying into the processing vessel an object to be processed having asurface on which an oxide film has been formed; supplying the active gasspecies produced by the active gas species generating unit onto theoxide film on the surface of the object; and allowing the active gasspecies to react with the oxide film under an unheated condition, inwhich the shielding plate is inserted into the gap to shield the heatradiation from the transparent window, in order to form areaction-product film.
 11. A processing method as claimed in claim 10further comprising: causing the shielding plate to extract from the gapafter the reaction-product film is formed, so that the heater heats thereaction-product film through the transparent window, in order toevaporate and remove the reaction-product film.
 12. A processing methodas claimed in claim 11, wherein the heater is actuated after thereaction-product film is formed.